Method and apparatus for requesting system information by using preamble in next generation mobile communication system

ABSTRACT

The present disclosure relates to a communication scheme for convergence of an IoT technology and a 5G communication system for supporting a higher data transmission rate beyond a 4G system, and a system therefor. The present disclosure may be applied to an intelligent service (for example, a smart home, a smart building, a smart city, a smart car or connected car, healthcare, digital education, retail business, a security and security related service, or the like) on the basis of a 5G communication technology and an IoT related technology. The present invention provides a method and an apparatus for efficiently transmitting or receiving system information by using a preamble in a next generation mobile communication system.

TECHNICAL FIELD

The present disclosure relates to a method and an apparatus foroperations of a UE and an eNB to request system information in anext-generation mobile communication system.

BACKGROUND ART

In order to meet wireless data traffic demands, which have increasedsince the commercialization of a 4G communication system, efforts todevelop an improved 5G communication system or a pre-5G communicationsystem have been made. For this reason, the 5G communication system orthe pre-5G communication system is called a beyond-4G-networkcommunication system or a post-LTE system. In order to achieve a highdata transmission rate, implementation of the 5G communication system inan mmWave band (for example, 60 GHz band) is being considered.

In the 5G communication system, technologies such as beamforming,massive MIMO, Full-Dimensional MIMO (FD-MIMO), array antenna, analogbeamforming, and large-scale antenna are being discussed as means tomitigate a propagation path loss in the mmWave band and increase apropagation transmission distance. Further, the 5G communication systemhas developed technologies such as an evolved small cell, an advancedsmall cell, a cloud Radio Access Network (RAN), an ultra-dense network,Device-to-Device communication (D2D), a wireless backhaul, a movingnetwork, cooperative communication, Coordinated Multi-Points (CoMP), andreceived interference cancellation in order to improve the systemnetwork.

In addition, the 5G system has developed advanced coding modulation(ACM) schemes, such as hybrid FSK and QAM modulation (FQAM) and slidingwindow superposition coding (SWSC), and advanced access technologies,such as filter bank multi carrier (FBMC), non-orthogonal multiple access(NOMA), and sparse code multiple access (SCMA).

The Internet has evolved from a human-oriented connection network inwhich humans generate and consume information to an Internet-of-Things(IoT) network in which information is exchanged between distributedcomponents such as objects and the like. Internet-of-Everything (IoE)technology, in which big-data processing technology is combined with IoTtechnology through a connection with a cloud server or the like, hasemerged. In order to implement IoT, technical factors such as a sensingtechnique, wired/wireless communication, network infrastructure,service-interface technology, and secure technology are required, andresearch on technologies such as a sensor network, machine-to-machine(M2M) communication, machine-type communication (MTC), and the like forconnection between objects has recently been conducted.

In an IoT environment, through collection and analysis of data generatedin connected objects, an intelligent Internet Technology (IT) servicethat creates new value in peoples' lives may be provided. The IoT may beapplied to fields such as those of a smart home, a smart building, asmart city, a smart car, a connected car, a smart grid, health care, asmart home appliance, or high-tech medical services through theconvergence of the conventional information technology (IT) and variousindustries.

Accordingly, various attempts to apply the 5G communication to the IoTnetwork are being made. For example, technologies such as a sensornetwork, machine-to-machine (M2M), and machine-type communication (MTC)are implemented using beamforming, MIMO, and array-antenna schemes. Theapplication of a cloud RAN as big-data processing technology may be anexample of convergence of 5G technology and IoT technology.

With the development of the next-generation mobile communication system,a new approach to and research on preamble transmission is spotlighted.Particularly, a new communication system requires improvement of amethod and an apparatus for smoothly performing a process oftransmitting a preamble to make a request for system information.

DISCLOSURE OF INVENTION Technical Problem

An aspect of the present disclosure is to propose a preamble making arequest for system information in a wireless communication system andpropose a series of processes for transmitting and receiving systeminformation through the proposed preamble.

Another aspect of the present disclosure is to propose a message makinga request for system information in a wireless communication system andpropose a series of processes for transmitting and receiving systeminformation through the proposed message.

Still another aspect of the present disclosure is to propose a method bywhich, when measuring a cell and reporting the result thereof, a UEtransmitting and receiving data simultaneously using a plurality ofradio access technologies (RATs) in a wireless communication systemprovides to make an eNB accurately add/release a cell and accuratelydetermine handover.

Solution to Problem

In accordance with an aspect of the present disclosure, a method of aneNB in a wireless communication system is provided. The method includes:transmitting a configuration message including information on aplurality of frequencies which are measurement objects and thresholdinformation of a signal intensity (reference signal received power(RSRP)) related to measurement of the plurality of frequencies to a UE;and receiving a measurement report message based on the configurationmessage from the UE, wherein the configuration message further includesindication information indicating the measurement for at least one ofthe plurality of frequencies regardless of the threshold information.

In accordance with another aspect of the present disclosure, a method ofa UE in a wireless communication system is provided. The methodincludes: receiving a configuration message including information on aplurality of frequencies which are measurement objects and thresholdinformation of reference signal received power (RSRP) related tomeasurement for the plurality of frequencies from an eNB; performingmeasurement, based on the configuration message; and transmitting ameasurement report message including a result of the performedmeasurement, based on the configuration message, to the eNB, wherein theconfiguration message further includes indication information indicatingthe measurement for at least one of the plurality of frequenciesregardless of the threshold information.

In accordance with another aspect of the present disclosure, an eNB in awireless communication system is provided. The eNB includes: atransceiver; and a controller configured to transmit a configurationmessage including information on a plurality of frequencies which aremeasurement objects and threshold information of a signal intensity(reference signal received power (RSRP)) related to measurement of theplurality of frequencies to a UE, perform measurement, based on theconfiguration message, and control the transceiver to receive ameasurement report message based on the configuration message from theUE, wherein the configuration message further includes indicationinformation indicating the measurement for at least one of the pluralityof frequencies regardless of the threshold information.

In accordance with another aspect of the present disclosure, a UE in awireless communication system is provided. The UE includes atransceiver, and a controller configured to control the transceiver toreceive a configuration message including information on a plurality offrequencies which are measurement objects and threshold information ofreference signal received power (RSRP) related to measurement for theplurality of frequencies from an eNB, perform measurement, based on theconfiguration message, and control the transceiver to transmit ameasurement report message including a result of the performedmeasurement, based on the configuration message, to the eNB, wherein theconfiguration message further includes indication information indicatingthe measurement for at least one of the plurality of frequenciesregardless of the threshold information.

In accordance with another aspect of the present disclosure, a method ofa UE in a wireless communication system is provided. The methodincludes: receiving first system information from an eNB; making arequest for second system information other than the first systeminformation through a selected message, based on the first systeminformation; and when the second system information is not received inresponse to the request, making a request for the second systeminformation again after a backoff time determined by a preset backoffindicator, wherein the backoff indicator is applied differentlyaccording to the selected message.

In accordance with another aspect of the present disclosure, a method ofan eNB in a wireless communication system is provided. The methodincludes: transmitting first system information to a UE; receiving arequest for second system information other than the first systeminformation from the UE through a selected message, based on the firstsystem information; and receiving, from the UE, a request for the secondsystem information again after a backoff time determined by a presetbackoff indicator, wherein the backoff indicator is applied differentlyaccording to the selected message.

In accordance with another aspect of the present disclosure, a UE in awireless communication system is provided. The UE includes: atransceiver; and a controller configured to receive first systeminformation from an eNB, make a request for second system informationother than the first system information through a selected message,based on the first system information; and when the second systeminformation is not received in response to the request, make a requestfor the second system information again after a backoff time determinedby a preset backoff indicator, wherein the backoff indicator is applieddifferently according to the selected message.

In accordance with another aspect of the present disclosure, an eNB in awireless communication system is provided. The eNB includes: atransceiver; and a controller configured to transmit first systeminformation to a UE, receive a request for second system informationother than the first system information from the UE through a selectedmessage, based on the first system information, and receive, from theUE, a request for the second system information again after a backofftime determined by a preset backoff indicator, wherein the backoffindicator is applied differently according to the selected message.

Advantageous Effects of Invention

According to an embodiment of the present disclosure, it is possible toimprove a message transmission/reception process between the UE and theeNB and thus smoothly and efficiently perform a system informationtransmission/reception process.

According to another embodiment of the present disclosure, the UEreduces power consumption required for measuring neighboring eNBs andmeasures and reports different types of eNBs in time, and thus the eNBmay add the corresponding measured eNB to the UE or move the UE to thecorresponding measured eNB, so that the UE can use the corresponding eNBin time.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A illustrates the structure of a next-generation mobilecommunication system;

FIG. 1B illustrates a method of providing system information in thenext-generation mobile communication system;

FIG. 1C illustrates a random access process in the conventional LTEsystem;

FIG. 1D illustrates a process of selecting an msg-1-based or anmsg-3-based SI request method according to the present disclosure;

FIG. 1E illustrates an msg-1-based SI request process according to thepresent disclosure;

FIG. 1F illustrates a method of indicating an SI-request-dedicatedpreamble according to the present disclosure;

FIG. 1G illustrates the format of a random access response messageaccording to the present disclosure;

FIG. 1H illustrates a method of configuring subheaders including abackoff indicator according to the present disclosure;

FIG. 1I is a flowchart illustrating the operation of the UE according tothe present disclosure;

FIG. 1J illustrates a method of indicating system information of atarget cell during a handover process according to the presentdisclosure;

FIG. 1K is a flowchart illustrating the operation of the UE indicatingsystem information of a target cell during a handover process accordingto the present disclosure;

FIG. 1L is a block diagram illustrating the internal structure of the UEto which the present disclosure is applied;

FIG. 1M is a block diagram illustrating the configuration of the eNBaccording to the present disclosure;

FIG. 2A illustrates the structure of a next-generation mobilecommunication system;

FIG. 2B illustrates a method of providing system information in thenext-generation mobile communication system;

FIG. 2C illustrates a random access process in the conventional LTEsystem;

FIG. 2D illustrates a process of selecting an msg-1-based or anmsg-3-based SI request method according to the present disclosure;

FIG. 2E illustrates an msg-3-based SI request process according to thepresent disclosure;

FIG. 2F illustrates a method of configuring an SI-request MAC CEaccording to the present disclosure;

FIG. 2G illustrates a method of configuring a UE ID MAC CE according tothe present disclosure;

FIG. 2H illustrates a method of configuring a UE contention resolutionidentity included in msg 4 according to the present disclosure;

FIG. 2l is a flowchart illustrating the operation of the UE according tothe present disclosure;

FIG. 2J illustrates a procedure of processing the case in which generalrandom access and SI-request random access overlap each other in thepresent disclosure;

FIG. 2K is a flowchart illustrating the operation of the UE when generalrandom access and SI-request random access overlap each other in thepresent disclosure;

FIG. 2L is a block diagram illustrating the internal structure of the UEto which the present disclosure is applied;

FIG. 2M is a block diagram illustrating the configuration of the eNBaccording to the present disclosure;

FIG. 3A illustrates the structure of the LTE system to be referred tofor description of the present disclosure;

FIG. 3B illustrates a wireless protocol structure of the LTE system tobe referred to for description of the present disclosure;

FIG. 3C illustrates the concept of multiple connections in LTE and NR;

FIG. 3D illustrates an example of message flow between the UE and eNBswhen the present disclosure is applied;

FIG. 3E is a flowchart illustrating the operation of the UE when thepresent disclosure is applied; and

FIG. 3F is a block diagram illustrating the UE according to anembodiment of the present disclosure.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present disclosure will be described indetail in conjunction with the accompanying drawings. In the followingdescription of the present disclosure, a detailed description of knownfunctions or configurations incorporated herein will be omitted when itmay make the subject matter of the present disclosure rather unclear.The terms which will be described below are terms defined inconsideration of the functions in the present disclosure, and may bedifferent according to users, intentions of the users, or customs.Therefore, the definitions of the terms should be made based on thecontents throughout the specification.

The advantages and features of the present disclosure and ways toachieve them will be apparent by making reference to embodiments asdescribed below in detail in conjunction with the accompanying drawings.However, the present disclosure is not limited to the embodiments setforth below, but may be implemented in various different forms. Thefollowing embodiments are provided only to completely disclose thepresent disclosure and inform those skilled in the art of the scope ofthe present disclosure, and the present disclosure is defined only bythe scope of the appended claims. Throughout the specification, the sameor like reference numerals designate the same or like elements.

First Embodiment

FIG. 1A illustrates the structure of a next-generation mobilecommunication system.

Referring to FIG. 1A, a radio access network of the next-generationmobile communication system includes a next-generation base station(hereinafter, referred to as NR NB (new radio node B)) 1 a-10 and a newradio core network (NR CN) 1 a-05 as illustrated in FIG. 1A. A userterminal (hereinafter, referred to as an NR UE (New Radio UserEquipment) or a UE) 1 a-15 accesses an external network through the NRNB 1 a-10 and the NR CN 1 a-05.

In FIG. 1A, the NR NB 1 a-10 corresponds to an evolved Node B (eNB) in aconventional LTE system. The NR NB may be connected to the NR UE 1 a-15through a radio channel and may provide better service compared to theconventional node B. Since all user traffic is served through a sharedchannel in the next-generation mobile communication system, a device forcollecting and scheduling status information of buffer statuses,available transmission power statuses, and channel statuses of UEs isrequired, which corresponds to the NR NB 1 a-10.

One NR NB generally controls a plurality of cells. The NR NB may have abandwidth wider than the conventional maximum bandwidth in order toimplement super-high-speed data transmission compared to conventionalLTE and may apply orthogonal frequency division multiplexing (OFDM)through radio access technology, and may further apply beamformingtechnology. Further, a modulation scheme and an adaptive modulation andcoding (hereinafter, referred to as an AMC) scheme of determining achannel coding rate are applied to the LTE system in correspondence to achannel status of the UE.

The NR CN 1 a-05 performs a function of supporting mobility, configuringa bearer, and configuring quality of service (QoS). The NR CN is adevice for performing a function of managing mobility of the UE andvarious control functions and is connected to a plurality of eNBs.Further, the next-generation mobile communication system may be linkedto the conventional LTE system, and the NR CN is connected to an MME 1a-25 through a network interface. The MME is connected to an eNB 1 a-30,which is the conventional eNB.

FIG. 1B illustrates a method of providing system information in thenext-generation mobile communication system.

In the next-generation mobile communication system, system informationbroadcasted by a gNB 1 b-10 is largely divided into minimum systeminformation (SI) and other system information.

The minimum SI is periodically broadcasted as indicated by referencenumeral 1 b-15 and includes configuration information required forinitial access and SI scheduling information required for receivingother SI, broadcasted periodically or in response to a request.Basically, the other SI includes all pieces of configuration informationthat are not included in the minimum SI.

The other SI is broadcasted periodically as indicated by referencenumeral 1 b-20 or in response to a request from the UE, or is providedto the UE through dedicated signaling, as indicated by reference numeral1 b-25. When the other SI is received through a UE request, the UE isrequired to identify whether the other SI is valid in the cell or iscurrently being broadcasted (by a request from another UE) before therequest. The identification can be performed through particularinformation provided by the minimum SI.

An idle-mode (RRC_IDLE) UE or an inactive-mode (RRC_INACTIVE) UE maymake a request for other SI without changing a current RRC state. Aconnected-mode (RRC_CONNECTED) UE may make a request for and receiveother SI through dedicated RRC signaling. The other SI is broadcasted ata predetermined cycle for a predetermined period of time. Public warningsystem (PWS) information is classified and provided as other SI. Whetherto broadcast the other SI or to provide the same to the UE throughdedicated RRC signaling is implemented by the network.

FIG. 1C illustrates a random access process in the conventional LTEsystem.

Random access is performed when uplink synchronization is performed ordata is transmitted to the network. More specifically, random access maybe performed when switching from an idle mode to a connected mode, whenRRC reestablishment is performed, when handover is performed, and whenuplink/downlink data transmission starts. Upon receiving a dedicatedpreamble from a gNB 1 c-10, a UE 1 c-05 applies and transmits thepreamble. Otherwise, the UE selects one of two preamble groups andselects the preamble belonging to the selected group. The groups arereferred to as group A and group B. If a channel quality status ishigher than a particular threshold value and the size of msg 3 is largerthan a particular threshold value, the UE selects a preamble belongingto group B and, otherwise, selects a preamble belonging to group A.

The preamble is transmitted in an n^(th) subframe, as indicated byreference numeral 1 c-15. When the preamble is transmitted in the n^(th)subframe, a random access response (RAR) window starts from an n+3^(th)subframe, and it is monitored whether the RAR is transmitted within thewindow time interval as indicated by reference numeral 1 c-20.Scheduling information of the RAR is indicated by an RA-RATI of a PDCCH.The RA-RNTI is induced using the location of radio resources on time andfrequency axes used for transmitting the preamble.

The RAR includes a timing advance command, a UL grant, and a temporaryC-RNTI. If the RAR is successfully received in the RAR window, msg 3 istransmitted using information of the UL grant included in the RAR, asindicated by reference numeral 1 c-25. Msg 3 includes different piecesof information depending on the purpose of the random access. [Table 1]below is an example of information carried on msg 3.

TABLE 1 CASE Message 3 Contents RRC CONNECTION CCCH SDU SETUP RRC RE-CCCH SDU, BSR (if grant is enough), ESTABLISHMENT PHR (if triggered &grant is enough) Handover C-RNTI CE, BSR, PHR, (part of) DCCH (randompreamble) SDU Handover BSR, PHR , (part of) DCCH SDU (dedicatedpreamble) UL resume C-RNTI CE, BSR, PHR, (part of) DCCH/DTCH SDU PDCCHC-RNTI CE, BSR, PHR, (part of) order (random DCCH/DTCH SDU preamble)PDCCH BSR, PHR, (part of) DCCH/DTCH SDU order (dedicated preamble)

If the RAR is received in an n^(th) subframe, msg 3 is transmitted in ann+6^(th) subframe. A hybrid auto retransmission request (HARQ) isapplied to msg 3 and thereafter. After msg 3 transmission, the UE drivesa particular timer and monitors a contention resolution (CR) messagebefore the timer expires, as indicated by reference numeral 1 c-30. TheCR message includes an RRC connection setup message or an RRC connectionreestablishment message depending on the purpose of the random access aswell as a CR medium access control (MAC) control element (CE).

FIG. 1D illustrates a process of selecting an msg 1- or msg-3-based SIrequest method according to the present disclosure.

In order to make a request for system information other than the minimumSI, the UE uses random access.

The UE makes a request for system information, which the UE desires toreceive, to the network through msg 1 (preamble) or msg 3. In step 1d-05, the UE determines whether PRACH resource information, which can beused for an SI request, is included in the periodically broadcastedminimum SI. The PRACH resource information may include preamble ID (orindex) information used for the SI request (prach-ConfigIndex) and radioresource information for transmitting the preamble.

When the information is included, the UE may make a request for systeminformation other than the minimum SI through msg 1, dedicated for theSI request, in step 1 d-10. Otherwise, the UE makes a request for systeminformation other than the minimum SI through msg 3 in step 1 d-15. Atthis time, the UE transmits the preamble used for the general randomaccess.

FIG. 1E illustrates an msg-1-based SI request process according to thepresent disclosure.

A UE 1 e-05 receives minimum SI from a network 1 e-10 in step 1 e-15.The minimum SI may include an ID (index) of a dedicated preamble usedfor the SI request and radio resource information for transmitting thepreamble.

The UE triggers a request for system information other than the minimumSI in step 1 e-20. The UE determines whether dedicated preambleinformation for the SI request is included in the minimum SI in step 1e-25.

If the dedicated preamble can be transmitted, the UE selects a preamblecorresponding to the requested system information in step 1 e-30 andtransmits the preamble to the network in step 1 e-35. The networktransmits the RAR to the UE for the purpose of acknowledgement (ACK) instep 1 e-40. The RAR may include one or more subheaders including abackoff indicator (BI).

The backoff indicator is used for deriving a backoff time during whichthe UE should wait to perform a reattempt when the UE fails in randomaccess. For example, one value may be selected from values between 0 andthe backoff indicator through uniform distribution and the selectedvalue may be configured to the backoff time. The subheader including theBI may be separately defined according to general random access, anmsg-1-based SI request, or an msg-3-based SI request.

A subheader including an ID of the transmitted preamble may be included,and a MAC RAR corresponding to the subheader may include radio resourceinformation through which the requested system information isbroadcasted. The radio resource information may be included in theminimum SI. The radio resources may be generally used for unicasttransmission, and if the UE makes a request for particular systeminformation, may be used for broadcasting the system information.

If the RAR is not received within the SI window or if the subheaderincluding the ID of the transmitted preamble is not included in thereceived RAR, it is considered that the preamble transmission hasfailed. Then, after waiting for the backoff time derived by thecorresponding BI, the UE may transmit the preamble for the SI requestagain. The UE successfully receives the relevant RAR in step 1 e-60 andthen receives the requested system information in the configured radioresources in step 1 e-65.

FIG. 1F illustrates a method of indicating an SI-request-dedicatedpreamble according to the present disclosure.

If 0^(th) to x^(th) preambles can be used in the next-generation mobilecommunication system, 0^(th) to k^(th) preambles may be classified aspreambles 1 f-05 or general random access, k+1^(th) to x−n+1^(th)preambles may be classified as dedicated preambles 1 f-10, and x-n^(th)to x^(th) preambles may be classified as preambles 1 f-15 for an SIrequest.

Each preamble for the SI request may be designated to be used for makinga request for particular system information. For example, among thepreambles for the SI request, the preamble corresponding to the lowestindex value may be used for making a request for all pieces of systeminformation except for minimum SI. The preamble corresponding to thenext index value may be used for making a request for system informationincluded in a first SI message. The preamble corresponding to the nextindex value may be used for making a request for system informationincluded in a second SI message. Alternatively, the SI message may bereplaced with a system information block (SIB).

FIG. 1G illustrates the format of a random access response messageaccording to the present disclosure.

In the mobile communication system, the RAR includes one or moresubheaders and one or more MAC RARs. In FIG. 1G, a MAC header 1 g-15including one or more subheaders is located at a front part of the RAR,but the subheaders may be located at another part of the RAR. Some ofthe subheaders may include a BI, as indicated by reference numeral 1g-05, and there may be no MAC RAR corresponding to the subheader.Further, in subheaders 1 g-10 including preamble IDs, one MAC RAR 1 g-20corresponding thereto exists.

FIG. 1H illustrates a method of configuring a subheader including abackoff indicator according to the present disclosure.

FIG. 1H(a) shows an E/T/R/R/BI MAC subheader in the conventional LTEtechnology. A field E 1 h-05 indicates whether there is another MACsubheader. A field T 1 h-10 is used for indicating whether thecorresponding subheader is a subheader including a BI 1 h-15 or asubheader including a random access preamble ID (RAPID). Field R is areserved bit. A field BI is used for deriving the backoff time and hasthe size of a total of 4 bits.

The present disclosure provides BIs separately for general randomaccess, random access for an msg-1-based SI request, and random accessfor an msg-3-based SI request. To this end, a field T1 1 h-20 indicatingwhich type of random access corresponds to the BI is added to the MACsubheader.

FIG. 1H(b) is an example of the MAC subheader proposed by the presentdisclosure. In the present embodiment, the conventional 2-bit field R isused as the field indicating which type of random access corresponds tothe BI.

FIG. 1H(c) illustrates some of the MAC header in which MAC subheadersincluding 3 types of BIs are arranged in a row. For example, a BI 1 h-30included in the corresponding MAC subheader is applied to general randomaccess if the field T1 is configured as 00 1 h-25, a BI 1 h-40 includedin the corresponding MAC subheader is applied to random access for themsg-1-based SI request if the field T1 is configured as 01 1 h-35, and aBI 1 h-50 included in the corresponding MAC subheader is applied torandom access for the msg-3-based SI request if the field T1 isconfigured as 10 1 h-45. If the field T1 is 11, the BI included in thecorresponding MAC subheader is applied to all types of random access.

In another embodiment, the BI may be applied only to the random accessfor the msg-3-based SI request without being applied to the randomaccess for the msg-1-based SI request.

FIG. 1I is a flowchart illustrating the operation of the UE according tothe present disclosure.

In step 1 i-05, the UE receives minimum SI including PRACH radioresources allocated for the SI request from the network. In step 1 i-10,the UE triggers an SI request process. In step 1 i-15, the UE selects apreamble for the SI request in consideration of an SI message or a SIBfor which the UE itself should make a request. In step 1 i-20, the UEtransmits the selected preamble for the SI request.

In step 1 i-25, the UE successfully receives an RAR. The RAR may includeone or more MAC subheaders including a BI. However, if a MAC subheaderincluding a BI which is applied to the random access for the msg-1-basedSI request is not received, the backoff time is considered to be 0. Instep 1 i-30, if it is considered that the random access is failed, theUE drives the derived backoff timer in consideration of the BIcorresponding to the type of the random access. If there is nocorresponding BI, the backoff time is considered to be 0.

In step 1 i-35, if the timer expires, the UE may transmit the preamblefor the SI request again. In step 1 i-40, the UE receives the requestedSI from the network.

FIG. 1J illustrates a method of indicating system information of atarget cell during handover according to the present disclosure.

A UE 1 j-05 receives minimum SI from a source gNB 1 j-10 in step 1 j-20.The UE may make a request for required SI to the source gNB throughconfiguration information required for an SI request included in theminimum SI in step 1 j-25. The source gNB transmits the requested SI tothe UE in step 1 j-30.

The source gNB determines to perform handover on the basis ofmeasurement information received from the UE and transmits an HO requestmessage to a target gNB 1 j-15 in step 1 j-35. The HO request messageincludes SI possessed by the UE. The target gNB transfers SI informationthat is required when the UE stays in the target gNB to the source gNBin step 1 j-40 on the basis of the SI.

The source gNB transmits an HO command message indicating handover tothe UE, and the message includes SI information required when the UEstays in the target gNB, SI information which the target gNB can reuseamong SI of the source gNB currently applied, and an indicatorindicating whether the SI request to the target gNB is needed in step 1j-45.

The UE successfully performs handover to the target gNB and transmits anHO complete message in step 1 j-50. The UE determines whether to performrandom access for the SI request to the target gNB in consideration ofSI-related information included in the HO command in step 1 j-55.Particularly, if the indicator indicates that the SI request to thetarget gNB is not needed, the SI request is not made. When the SIrequest to the target gNB is needed, the UE performs the random accessfor the SI request to the target gNB in step 1 j-60.

FIG. 1K is a flowchart illustrating an operation of the UE indicatingsystem information of a target cell during a handover process accordingto the present disclosure.

The UE receives an HO command message indicating handover from thenetwork, and the message includes SI information required when the UEstays in the target gNB, SI information which the target gNB can reuseamong the currently applied SI of the source gNB, and an indicatorindicating whether the SI request to the target gNB is needed in step1K-05.

In step 1 k-10, the UE completes the operation of handover to the targetcell. In step 1 k-15, the UE determines whether the SI request to thetarget cell is needed in consideration of the SI-related information. Instep 1 k-20, if the indicator indicates that the SI request is notneeded, the UE reuses the current SI information and does not make theSI request.

FIG. 1L illustrates the structure of the UE.

Referring to FIG. 1L, the UE includes a radio-frequency (RF) processingunit 1 l-10, a baseband processing unit 1 l-20, a storage unit 1 l-30,and a controller 1 l-40.

The RF processing unit 1 l-10 performs a function for transmitting andreceiving a signal through a radio channel, such as band conversion andamplification of a signal. That is, the RF processing unit 1 l-10up-converts a baseband signal provided from the baseband processing unit1 l-20 into an RF band signal, transmits the RF band signal through anantenna, and then down-converts the RF band signal received through theantenna into a baseband signal. For example, the RF processing unit 1l-10 may include a transmission filter, a reception filter, anamplifier, a mixer, an oscillator, a digital-to-analog converter (DAC),an analog-to-digital converter (ADC), and the like. Although FIG. 1Lillustrates only one antenna, the UE may include a plurality ofantennas.

In addition, the RF processing unit 1 l-10 may include a plurality of RFchains. Moreover, the RF processing unit 1 l-10 may perform beamforming.For the beamforming, the RF processing unit 1 l-10 may control the phaseand the size of each signal transmitted/received through a plurality ofantennas or antenna elements. Further, the RF processing unit mayperform multiple-input multiple-output (MIMO) operation and receive aplurality of layers during MIMO operation.

The baseband processing unit 1 l-20 performs a function of performingconversion between a baseband signal and a bitstream according to aphysical layer standard of the system. For example, in datatransmission, the baseband processing unit 1 l-20 generates complexsymbols by encoding and modulating a transmission bitstream.

In addition, the baseband processing unit 1 l-20, when receiving data,reconstructs a reception bitstream through the demodulation and decodingof a baseband signal provided from the RF processing unit 1 l-10. Forexample, in an orthogonal-frequency-division-multiplexing (OFDM) scheme,when data is transmitted, the baseband processing unit 1 l-20 generatescomplex symbols by encoding and modulating a transmission bitstream,maps the complex symbols to subcarriers, and then configures OFDMsymbols through an inverse fast Fourier transform (IFFT) operation and acyclic prefix (CP) insertion.

Further, in data reception, the baseband processing unit 1 l-20 dividesthe baseband signal provided from the RF processing unit 1310 in unitsof OFDM symbols, reconstructs the signals mapped to the subcarriersthrough a fast Fourier transform (FFT) operation, and then reconstructsthe reception bitstream through demodulation and decoding.

The baseband processing unit 1 l-20 and the RF processing unit 1 l-10transmit and receive the signal as described above. Accordingly, thebaseband processing unit 1 l-20 and the RF processing unit 1 l-10 may bereferred to as a transmitter, a receiver, a transceiver, or acommunication unit.

Further, at least one of the baseband processing unit 1 l-20 and the RFprocessing unit 1 l-10 may include a plurality of communication modulesto support a plurality of different radio access technologies. Inaddition, at least one of the baseband processing unit 1 l-20 and the RFprocessing unit 1 l-10 may include different communication modules toprocess signals of different frequency bands. For example, the differentradio access technologies may include a wireless LAN (for example, IEEE802.11) and a cellular network (for example, LTE). Further, thedifferent frequency bands may include a super-high-frequency (SHF) (forexample, 2.5 GHz and 2 GHz) band and a millimeter (mm)-wave (forexample, 60 GHz) band.

The storage unit 1 l-30 stores data such as a basic program, anapplication program, and setting information for the operation of theUE. Particularly, the storage unit 1 l-30 may store information relatedto a second access node for performing wireless communication through asecond radio access technology. The storage unit 1 l-30 provides storeddata according to a request from the controller 1 l-40.

The controller 1 l-40 controls the overall operation of the UE. Forexample, the controller 1 l-40 transmits and receives a signal throughthe baseband processing unit 1 l-20 and the RF processing unit 1 l-10.Further, the controller 1 l-40 records data in the storage unit 1 l-40and reads the data. To this end, the controller 1 l-40 may include atleast one processor. For example, the controller 1 l-40 may include acommunication processor (CP), which performs control for communication,and an application processor (AP), which controls a higher layer such asan application program.

FIG. 1M is a block diagram of an MeNB in a wireless communication systemaccording to an embodiment of the present disclosure.

As illustrated in FIG. 1M, the eNB includes an RF processing unit 1m-10, a baseband processing unit 1 m-20, a backhaul communication unit 1m-30, a storage unit 1 m-40, and a controller 1 m-50.

The RF processing unit 1 m-10 performs a function for transmitting andreceiving a signal through a wireless channel, such as band conversionand amplification of a signal. That is, the RF processing unit 1 m-10up-converts a baseband signal provided from the baseband processing unit1 m-20 into an RF band signal, transmits the RF band signal through anantenna, and then down-converts the RF band signal received through theantenna into a baseband signal. For example, the RF processing unit 1m-10 may include a transmission filter, a reception filter, anamplifier, a mixer, an oscillator, a DAC, and an ADC. Although FIG. 1Millustrates only one antenna, the first access node may include aplurality of antennas.

In addition, the RF processing unit 1 m-10 may include a plurality of RFchains. The RF processing unit 1 m-10 may perform beamforming. For thebeamforming, the RF processing unit 1 m-10 may control the phase and thesize of each of the signals transmitted and received through a pluralityof antennas or antenna elements. The RF processing unit may perform adownlink MIMO operation by transmitting one or more layers.

The baseband processing unit 1 m-20 performs a function of performingconversion between a baseband signal and a bitstream according to aphysical layer standard of the first radio access technology. Forexample, in data transmission, the baseband processing unit 1 m-20generates complex symbols by encoding and modulating a transmissionbitstream. In addition, in data reception, the baseband processing unit1 m-20 recovers a reception bit string through the demodulation anddecoding of a baseband signal provided from the RF processing unit 1m-10. For example, in an OFDM scheme, when data is transmitted, thebaseband processing unit 1 m-20 generates complex symbols by encodingand modulating the transmission bitstream, maps the complex symbols tosubcarriers, and then configures OFDM symbols through an IFFT operationand CP insertion.

Further, in data reception, the baseband processing unit 1 m-20 dividesthe baseband signal provided from the RF processing unit 1 m-10 in unitsof OFDM symbols, reconstructs the signals mapped to the subcarriersthrough an FFT operation, and then reconstructs the reception bitstreamthrough demodulation and decoding. The baseband processing unit 1 m-20and the RF processing unit 1 m-10 transmit and receive the signal asdescribed above. Accordingly, the baseband processing unit 1 m-20 andthe RF processing unit 1 m-10 may be referred to as a transmitter, areceiver, a transceiver, a communication unit, or a wirelesscommunication unit.

The backhaul communication unit 1 m-30 provides an interface forcommunicating with other nodes within the network. That is, the backhaulcommunication unit 1 m-30 converts a bitstream transmitted to anothernode, for example, another BS or a core network, from the BS into aphysical signal and converts the physical signal received from the othernode into the bitstream.

The storage unit 1 m-40 stores a basic program, an application program,and data such as configuration information for the operation of theMeNB. Particularly, the storage unit 1 m-40 may store information on abearer allocated to the accessed UE and a measurement result reportedfrom the accessed UE. Further, the storage unit 1 m-40 may storeinformation which is a reference for determining whether to allow orinterrupt multiple accesses to the UE. The storage unit 1 m-40 providesstored data according to a request from the controller 1 m-50.

The controller 1 m-50 controls the overall operation of the MeNB. Forexample, the controller 1 m-50 transmits and receives a signal throughthe baseband processing unit 1 m-20 and the RF processing unit 1 m-10 orthe backhaul communication unit 1 m-30. Further, the controller 1 m-50records data in the storage unit 1 m-40 and reads the data. To this end,the controller 1 m-50 may include at least one processor.

Second Embodiment

FIG. 2A illustrates the structure of a next-generation mobilecommunication system.

Referring to FIG. 2A, a radio access network of the next-generationmobile communication system includes a next-generation base station(hereinafter, referred to as new radio node B (NR NB) 2 a-10 and a newradio core network (NR CN) 2 a-05 as illustrated in FIG. 2A. A userterminal (hereinafter, referred to as a new radio user equipment (NR UE)or a UE) 2 a-15 accesses an external network through the NR NB 2 a-10and the NR CN 2 a-05.

In FIG. 2A, the NR NB 2 a-10 corresponds to an evolved Node B (eNB) ofthe conventional LTE system. The NR NB may be connected to the NR UE 2a-15 through a radio channel and may provide better service than aconventional node B. Since all user traffic is served through a sharedchannel in the next-generation mobile communication system, a device forcollecting and scheduling status information of buffer statuses,available transmission power statuses, and channel statuses of UEs isrequired, which corresponds to the NR NB 2 a-10.

One NR NB generally controls a plurality of cells. The NR NB may have abandwidth wider than the conventional maximum bandwidth in order toimplement super-high-speed data transmission compared to conventionalLTE and may apply orthogonal frequency division multiplexing (OFDM)through radio access technology and further apply beamformingtechnology. Further, a modulation scheme and an adaptive modulation andcoding (hereinafter, referred to as an AMC) scheme of determining achannel coding rate are applied to the LTE system in accordance with thechannel status of the UE.

The NR CN 2 a-05 performs a function of supporting mobility, configuringa bearer, and configuring QoS. The NR CN is a device for performing afunction of managing the mobility of the UE and various controlfunctions, and is connected to a plurality of eNBs. Further, thenext-generation mobile communication system may be linked to theconventional LTE system, and the NR CN is connected to an MME 2 a-25through a network interface. The MME is connected to an eNB 2 a-30,which is a conventional eNB.

FIG. 2B illustrates a method of providing system information in thenext-generation mobile communication system.

In the next-generation mobile communication system, system informationbroadcasted by a gNB 2 b-10 is largely divided into minimum systeminformation (SI) and other system information.

The minimum SI is periodically broadcasted, as indicated by referencenumeral 2 b-15, and includes configuration information required forinitial access and SI scheduling information required for receivingother SI, broadcasted periodically or in response to a request.

Basically, the other SI includes all pieces of configuration informationthat are not included in the minimum SI. The other SI is broadcastedperiodically as indicated by reference numeral 2 b-20 or in response toa request from the UE, or is provided to the UE through dedicatedsignaling, as indicated by reference numeral 2 b-25. When the other SIis received through a UE request, the UE is required to identify whetherthe other SI is valid in the cell or is currently being broadcasted (bya request from another UE) before the request. The identification can beperformed through particular information provided by the minimum SI.

An idle-mode (RRC_IDLE) UE or an inactive-mode (RRC_INACTIVE) UE maymake a request for other SI without changing a current RRC state. Aconnected-mode (RRC_CONNECTED) UE may make a request for and receiveother SI through dedicated RRC signaling. The other SI is broadcasted ata predetermined cycle for a predetermined period of time. Public warningsystem (PWS) information is classified and provided as other SI. Whetherto broadcast the other SI or to provide the same to the UE throughdedicated RRC signaling is implemented by the network.

FIG. 2C illustrates a random access process in a conventional LTEsystem.

Random access is performed when uplink synchronization is performed orwhen data is transmitted to the network. More specifically, randomaccess may be performed when switching from an idle mode to a connectedmode, when RRC reestablishment is performed, when handover is performed,and when uplink/downlink data transmission starts.

Upon receiving a dedicated preamble from a gNB 2 c-10, a UE 2 c-05applies and transmits the preamble. Otherwise, the UE selects one of twopreamble groups and selects a preamble belonging to the selected group.The groups are referred to as group A and group B. If a channel qualitystatus is higher than a particular threshold value and the size of msg 3is larger than a particular threshold value, the UE selects the preamblebelonging to group B and, otherwise, selects the preamble belonging togroup A.

The preamble is transmitted in an n^(th) subframe as indicated byreference numeral 2 c-15. When the preamble is transmitted in the n^(th)subframe, an RAR window starts from an n+3^(th) subframe and it ismonitored whether the RAR is transmitted within the window time intervalas indicated by reference numeral 2 c-20. Scheduling information of theRAR is indicated by an RA-RATI of a PDCCH. The RA-RNTI is induced usingthe location of radio resources on time and frequency axes used fortransmitting the preamble. The RAR includes a timing advance command, aUL grant, and a temporary C-RNTI.

If the RAR is successfully received in the RAR window, msg 3 istransmitted using information of the UL grant included in the RAR, asindicated by reference numeral 2 c-25. Msg 3 includes different piecesof information depending on the purpose of the random access. [Table 2]below is an example of information carried on msg 3.

TABLE 2 CASE Message 3 Contents RRC CONNECTION CCCH SDU SETUP RRC RE-CCCH SDU, BSR (if grant is enough), ESTABLISHMENT PHR (if triggered &grant is enough) Handover C-RNTI CE, BSR, PHR, (part of) DCCH (randompreamble) SDU Handover BSR, PHR, (part of) DCCH SDU (dedicated preamble)UL resume C-RNTI CE, BSR, PHR, (part of) DCCH/DTCH SDU PDCCH C-RNTI CE,BSR, PHR, (part of) order (random DCCH/DTCH SDU preamble) PDCCH BSR,PHR, (part of) DCCH/DTCH SDU order (dedicated preamble)

If the RAR is received in an n^(th) subframe, msg 3 is transmitted in ann+6^(th) subframe. HARQ is applied to msg 3 and thereafter. After msg 3transmission, the UE drives a particular timer and monitors a contentionresolution (CR) message before the timer expires, as indicated byreference numeral 2 c-30. The CR message includes an RRC connectionsetup message or an RRC connection reestablishment message depending onthe purpose of the random access as well as a CR MAC CE.

FIG. 2D illustrates a process of selecting an msg 1- or msg-3-based SIrequest method according to the present disclosure.

In order to make a request for system information other than the minimumSI, the UE uses random access. The UE makes a request for systeminformation, which the UE desires to receive, to the network through msg1 (preamble) or msg 3. In step 2 d-05, the UE determines whether PRACHresource information, which can be used for an SI request, is includedin the periodically broadcasted minimum SI.

The PRACH resource information may include preamble ID (or index)information used for the SI request (prach-ConfigIndex) and radioresource information for transmitting the preamble. If the minimum SIincludes the information, the UE may make a request for systeminformation other than the minimum SI through msg 1 for the SI requestin step 2 d-10. Otherwise, the UE makes a request for system informationother than the minimum SI through msg 3 in step 2 d-15. At this time,the UE transmits the preamble used for the general random access.

FIG. 2E illustrates an msg-3-based SI request process according to thepresent disclosure.

A UE 2 e-05 receives minimum SI from a network 2 e-10 in step 2 e-15.The UE triggers a request for system information other than the minimumSI in step 2 e-20. The UE determines whether dedicated preambleinformation for the SI request is included in the minimum SI in step 2e-25. If the dedicated preamble information is not included, the UEmakes a request for SI through msg 3 in step 2 e-30.

The UE transmits a preamble to the network in step 2 e-35. The preambleis not necessarily a preamble for the SI request. The UE receives arandom access response message for the preamble from the network in step2 e-40. The UE transmits msg 3 to the network in step 2 e-45. Msg 3includes information indicating which type of SI message or SIB isrequested by the UE.

Further, configured MAC CE information varies depending on the RRC stateof the UE. When the UE is in the connected mode, msg 3 includes a C-RNTIMAC CE and a MAC CE including SI request information (hereinafter,referred to as an SI-request MAC CE). The C-RNTI MAC CE includes C-RNTIinformation used for indicating a UE within a cell in the connectedmode. While the size of the C-RNTI MAC CE is 2 bytes in LTE technology,the size may be larger in a next-generation mobile communication system.

When the UE is in the idle mode or the inactive mode, msg 3 includes aUE ID MAC CE and an SI-request MAC CE. The UE ID MAC CE includes UE IDinformation used for indicating a UE within a cell in the idle mode orthe inactive mode. The UE ID information is used for determiningwhether, when the UE receives msg-4-message, the message corresponds tomsg 3, which the UE transmitted.

When the UE is in the connected mode, the network receiving msg 3transmits msg 4, scheduled with the C-RNTI, to the UE. When the UE is inthe idle mode or the inactive mode, the network receiving msg 3transmits msg 4 including the UE ID MAC CE and the SI-request MAC CE,which were included in msg 3 to the UE.

FIG. 2F illustrates a method of configuring an SI-request MAC CE in thepresent disclosure.

The SI-request MAC CE has a variable size according to the number ofrequested SI messages or SIBs. Each bit is mapped to the SI message orSIB to be requested. The UE configures the corresponding bit as “1” andinforms the network which SI message or SIB is requested. Further, aparticular position bit may be used for indicating whether all SImessages or SIBs except for the minimum SI are requested, as indicatedby reference numeral 2 f-05.

FIG. 2G illustrates a method of configuring a UE ID MAC CE in thepresent disclosure.

The UE ID MAC CE 2 g-05 has the same size as the C-RNTI MAC CE andincludes one random value generated by the UE or a value derived fromthe UE ID. The UE ID MAC CE includes UE ID information used forindicating a UE within a cell in the idle mode or the inactive mode. TheUE ID information is used for determining whether, when the UE receivesmsg 4, the message corresponds to msg 3, which the UE transmitted.

FIG. 2H illustrates a method of configuring a UE contention resolutionidentity included in msg 4 according to the present disclosure.

When the UE makes a request for SI in the idle mode or the inactivemode, the UE Contention Resolution Identity MAC CE 2 h-05 is included inmsg 4, which is a response message to msg 3. Information contained inthe MAC CE having the fixed size is the UE ID CE and the SI-request MACCE included in msg 3 or the UE ID MAC CE alone. When both the UE ID MACCE and the SI-request MAC CE are included, the UE contention resolutionidentity MAC CE may be exceeded due to the variable size of theSI-request MAC CE, in which case the exceeded information is notincluded in the MAC CE. When only the UE ID MAC CE is included, the sizeof the UE contention resolution identity MAC CE is defined to be thesame as the UE ID MAC CE.

FIG. 2l is a flowchart illustrating the operation of the UE according tothe present disclosure.

In step 2 i-05, the UE receives minimum SI. The minimum SI does notinclude msg 1 configuration information for an SI request. In step 2i-10, the UE triggers an SI request process through msg 3. In step 2i-15, the UE selects one preamble. In step 2 i-20, the UE transmits theselected preamble.

In step 2 i-25, the UE receives a random access response messagecorresponding to the preamble from the eNB. In step 2 i-30, the UEtransmits msg 3 to the eNB using scheduling information included in theresponse message. When the UE is in the connected mode, a C-RNTI MAC CEand an SI-request MAC CE are included in msg 3. When the UE is in theidle mode or the inactive mode, a UE ID MAC CE and an SI-request MAC CEare included in msg3.

In step 2 i-35, the UE receives msg 4. The UE receives msg 4 scheduledwith the C-RNTI when the UE is in the connected mode and receives msg 4including both the UE ID MAC CE and the SI-request MAC CE or only the UEID MAC CE when the UE is in the idle mode or the inactive mode. In step2 i-40, the UE receives requested system information.

FIG. 2J illustrates a procedure of processing the case in which generalrandom access and SI request random access overlap each other in thepresent disclosure.

In the present disclosure, when general random access and SI-requestrandom access overlap each other, general random access ispreferentially performed. Necessary system information related tonetwork connection may be included in the minimum SI and the remainingsystem information may be acquired through the UE request. According,when random access for connection to the network is triggered, it ispreferable to perform the SI request in preference to the random access.

A UE 2 j-05 receives minimum SI from a source gNB 2 j-10 in step 2 j-15.The minimum SI may include PRACH radio resource information for the SIrequest. The UE triggers a request for system information other than theminimum SI in step 2 j-20. The UE determines whether preambleinformation dedicated for the SI request is included in the minimum SIin step 2 j-25. If the preamble information is included, the SI isrequested using the SI-request-dedicated preamble. If the preambleinformation is not included, the UE makes a request for SI through msg 3in step 2 j-30. If the SI request process is triggered, or duringexecution of the process, the UE determines whether general randomaccess is triggered by the following causes in step 2 j-35.

Idle to connected mode transition: RRC CONNECTION REQUEST

RRC connection re-establishment: RRC CONNECTION REESTABLISHMENT REQUEST

HO complete: RRC CONNECTION RECONFIGURATION COMPLETE

DL data resume: PDCCH order

UL data resume: BSR is triggered

When the general random access is triggered, the UE stops the SI requestprocess triggered or being executed, and starts the general randomaccess in step 2 j-40. The UE transmits a preamble for the generalrandom access to the network.

FIG. 2K is a flowchart illustrating the operation of the UE when generalrandom access and SI-request random access overlap each other in thepresent disclosure.

In step 2 k-05, the UE receives minimum SI from the eNB. The minimum SImay include PRACH radio resource information for the SI request. In step2 k-10, the UE triggers a request for system information other than theminimum SI. If the SI-request process is triggered or during theSI-request process, the UE determines whether general random access istriggered by the following causes in step 2 k-15.

Idle to connected mode transition: RRC CONNECTION REQUEST

RRC connection re-establishment: RRC CONNECTION REESTABLISHMENT REQUEST

HO complete: RRC CONNECTION RECONFIGURATION COMPLETE

DL data resume: PDCCH order

UL data resume: BSR is triggered

If general random access is triggered, the UE stops the triggeredSI-request process or the triggered SI-request process being executedand starts general random access in step 2 k-20.

FIG. 2L illustrates the structure of the UE.

Referring to FIG. 2L, the UE includes a radio-frequency (RF) processingunit 2 l-10, a baseband processing unit 2 l-20, a storage unit 2 l-30,and a controller 2 l-40.

The RF processing unit 2 l-10 performs a function for transmitting andreceiving a signal through a wireless channel, such as band conversionand amplification of a signal. That is, the RF processing unit 2 l-10up-converts a baseband signal provided from the baseband processing unit2 l-20 into an RF band signal, transmits the RF band signal through anantenna, and then down-converts the RF band signal received through theantenna into a baseband signal. For example, the RF processing unit 2l-10 may include a transmission filter, a reception filter, anamplifier, a mixer, an oscillator, a Digital-to-Analog Converter (DAC),an Analog-to-Digital Converter (ADC), and the like. Although FIG. 2lillustrates only one antenna, the UE may include a plurality ofantennas.

In addition, the RF processing unit 2 l-10 may include a plurality of RFchains. Moreover, the RF processing unit 2 l-10 may perform beamforming.For the beamforming, the RF processing unit 2 l-10 may control the phaseand the size of each signal transmitted/received through a plurality ofantennas or antenna elements. The RF processing unit may perform MIMOand receive a plurality of layers during the MIMO operation.

The baseband processing unit 2 l-20 performs a function of performingconversion between a baseband signal and a bitstream according to thephysical layer standard of the system. For example, the basebandprocessing unit 2 l-20, when transmitting data, generates complexsymbols by encoding and modulating a transmission bitstream. Inaddition, in data reception, the baseband processing unit 2 l-20reconstructs a reception bitstream through the demodulation and decodingof a baseband signal provided from the RF processing unit 2 l-10. Forexample, in an orthogonal-frequency-division-multiplexing (OFDM) scheme,when data is transmitted, the baseband processing unit 2 l-20 generatescomplex symbols by encoding and modulating a transmission bitstream,maps the complex symbols to subcarriers, and then configures OFDMsymbols through an inverse fast Fourier transform (IFFT) operation and acyclic prefix (CP) insertion.

Further, in data reception, the baseband processing unit 2 l-20 dividesthe baseband signal provided from the RF processing unit 2 l-10 in unitsof OFDM symbols, reconstructs the signals mapped to the subcarriersthrough a fast Fourier transform (FFT) operation, and then reconstructsthe reception bitstream through demodulation and decoding.

The baseband processing unit 2 l-20 and the RF processing unit 2 l-10transmit and receive the signal as described above. Accordingly, thebaseband processing unit 2 l-20 and the RF processing unit 2 l-10 may bereferred to as a transmitter, a receiver, a transceiver, or acommunication unit. Further, at least one of the baseband processingunit 2 l-20 and the RF processing unit 2 l-10 may include a plurality ofcommunication modules to support a plurality of different radio accesstechnologies.

In addition, at least one of the baseband processing unit 2 l-20 and theRF processing unit 2 l-10 may include different communication modules toprocess signals of different frequency bands. For example, the differentradio access technologies may include a wireless LAN (for example, IEEE802.11) and a cellular network (for example, LTE). Further, thedifferent frequency bands may include a super-high-frequency (SHF) (forexample, 2.5 GHz and 2 GHz) band and a millimeter (mm) wave (forexample, 60 GHz) band.

The storage unit 2 l-30 stores data such as a basic program, anapplication program, and setting information for the operation of theUE. Particularly, the storage unit 2 l-30 may store information relatedto a second access node for performing wireless communication through asecond radio access technology. The storage unit 2 l-30 provides storeddata in response to a request from the controller 2 l-40.

The controller 2 l-40 controls the overall operation of the UE. Forexample, the controller 2 l-40 transmits and receives a signal throughthe baseband processing unit 2 l-20 and the RF processing unit 2 l-10.Further, the controller 2 l-40 records data in the storage unit 2 l-40and reads the data. To this end, the controller 2 l-40 may include atleast one processor. For example, the controller 2 l-40 may include acommunication processor (CP), which performs control for communication,and an application processor (AP), which controls a higher layer such asan application program.

FIG. 2M is a block diagram of an MeNB in a wireless communication systemaccording to an embodiment of the present disclosure.

As illustrated in FIG. 2M, the eNB includes an RF processing unit 2m-10, a baseband processing unit 2 m-20, a backhaul communication unit 2m-30, a storage unit 2 m-40, and a controller 2 m-50.

The RF processing unit 2 m-10 performs a function for transmitting andreceiving a signal through a wireless channel, such as band conversionand amplification of a signal. That is, the RF processing unit 2 m-10up-converts a baseband signal provided from the baseband processing unit2 m-20 into an RF band signal, transmits the RF band signal through anantenna, and then down-converts the RF band signal received through theantenna into a baseband signal. For example, the RF processing unit 2m-10 may include a transmission filter, a reception filter, anamplifier, a mixer, an oscillator, a DAC, and an ADC. Although FIG. 2Millustrates only one antenna, the first access node may include aplurality of antennas.

In addition, the RF processing unit 2 m-10 may include a plurality of RFchains. The RF processing unit 2 m-10 may perform beamforming. For thebeamforming, the RF processing unit 2 m-10 may control the phase andsize of each of the signals transmitted and received through a pluralityof antennas or antenna elements. The RF processing unit may perform adownlink MIMO operation by transmitting one or more layers.

The baseband processing unit 2 m-20 performs a function of performingconversion between a baseband signal and a bitstream according to aphysical layer standard of the radio access technology. For example, indata transmission, the baseband processing unit 2 m-20 generates complexsymbols by encoding and modulating a transmission bitstream. Inaddition, in data reception, the baseband processing unit 2 m-20reconstructs a reception bit string through the demodulation anddecoding of a baseband signal provided from the RF processing unit 2m-10. For example, in an OFDM scheme, when data is transmitted, thebaseband processing unit 2 m-20 may generate complex symbols by encodingand modulating the transmission bitstream, map the complex symbols tosubcarriers, and then configure OFDM symbols through an IFFT operationand CP insertion.

Further, in data reception, the baseband processing unit 2 m-20 dividesthe baseband signal provided from the RF processing unit 2 m-10 in unitsof OFDM symbols, reconstructs the signals mapped to the subcarriersthrough an FFT operation, and then reconstructs the reception bitstreamthrough demodulation and decoding. The baseband processing unit 2 m-20and the RF processing unit 2 m-10 transmit and receive the signal asdescribed above. Accordingly, the baseband processing unit 2 m-20 andthe RF processing unit 2 m-10 may be referred to as a transmitter, areceiver, a transceiver, a communication unit, or a wirelesscommunication unit.

The backhaul communication unit 2 m-30 provides an interface forcommunicating with other nodes within the network. That is, the backhaulcommunication unit 2 m-30 converts a bitstream transmitted to anothernode, for example, the SeNB or a core network from the MeNB, into aphysical signal and converts the physical signal received from the othernode into the bitstream.

The storage unit 2 m-40 stores a basic program, an application, and datasuch as configuration information for the operation of the MeNB.Particularly, the storage unit 2 m-40 may store information on a bearerallocated to the accessed UE and a measurement result reported from theaccessed UE. Further, the storage unit 2 m-40 may store informationwhich is a reference for determining whether to allow or interruptmultiple accesses to the UE. The storage unit 2 m-40 provides storeddata according to a request from the controller 2 m-50.

The controller 2 m-50 controls the overall operation of the MeNB. Forexample, the controller 2 m-50 transmits and receives a signal throughthe baseband processing unit 2 m-20 and the RF processing unit 2 m-10 orthrough the backhaul communication unit 2 m-30. Further, the controller2 m-50 records data in the storage unit 2 m-40 and reads the data. Tothis end, the controller 2 m-50 may include at least one processor.

Third Embodiment

In the following description, terms for identifying an access node,terms referring to network entities, terms referring to messages, termsreferring to interfaces between network entities, and terms referring tovarious pieces of identification information are used for convenience ofdescription. Therefore, the present disclosure is not limited by theterminologies provided below, and other terms that indicate subjectshaving equivalent technical meanings may be used.

For convenience of description, the present disclosure uses terms andnames defined in 3^(rd)-generation partnership project long-termevolution (3GPP LTE) standard and LTE-advanced (LTE-A) standards, whichare the latest standards among existing communication standards.However, the present disclosure is not limited to the terms and names,and may be equally applied to a system according to another standard.Particular, the present disclosure may be applied to 3GPP new radio (NR,5^(th)-generation mobile communication standard).

FIG. 3A illustrates the structure of the LTE system to be referred tofor description of the present disclosure.

Referring to FIG. 3A, the wireless communication system includes aplurality ofENBs 3 a-05, 3 a-10, 3 a-15, and 3 a-20, a mobilitymanagement entity (MME) 3 a-20, and a serving gateway (S-GW) 3 a-30. AUser Equipment (hereinafter, referred to as a UE or a terminal) 3 a-35accesses an external network through the ENBs 3 a-05, 3 a-10, 3 a-15,and 3 a-20 and the S-GW 3 a-30.

The ENBs 3 a-05, 3 a-10, 3 a-15, and 3 a-20 provide radio access to UEswhich access the network as access nodes of the cellular network. Thatis, in order to serve traffic of users, the ENBs 3 a-05, 3 a-10, 3 a-15,and 3 a-20 perform scheduling on the basis of collected statusinformation such as buffer statuses, available transmission powerstatuses, and channel statuses of UEs and support connection between theUEs and a core network (CN).

The MME 3 a-25 is a device performing a function of managing themobility of the UE and various control functions and is connected to aplurality of ENBs, and the S-GW 3 a-30 is a device providing a databearer. The MME 3 a-25 and the S-GW 3 a-30 further performauthentication for the UE accessing the network and bearer management,and process packets received from the ENBs 3 a-05, 3 a-10, 3 a-15, and 3a-20 or packets to be transferred to the ENBs 3 a-05, 3 a-10, 3 a-15,and 3 a-20.

FIG. 3B illustrates a wireless protocol structure of the LTE system tobe referred to for description of the present disclosure. The structureof the NR defined below may be different from the wireless protocolstructure in FIG. 3B, but the wireless protocol structure will bedescribed for convenience of the present disclosure.

Referring to FIG. 3B, the UE and the ENB includes packet dataconvergence protocols (PDCPs) 3 b-05 and 3 b-40, radio link controls(RLCs) 3 b-10 and 3 b-35, and medium access controls (MACs) 3 b-15 and 3b-30, respectively, in the wireless protocol of the LTE system.

The packet data convergence protocols (PDCPs) 3 b-05 and 3 b-40 performan operation of compressing/reconstructing an IP header, and the radiolink controls (RLCs) 3 b-10 and 3 b-35 reconfigure a PDCP Packet dataunit (PDU) to have a proper size. The MACs 3 b-15 and 3 b-30 areconnected with various RLC layer devices included in one UE, and performan operation for multiplexing RLC PDUs to the MAC PDU andde-multiplexing the RLC PDUs from the MAC PDU.

The PHY layers 3 b-20 and 3 b-25 perform an operation for channel-codingand modulating higher-layer data to generate an OFDM symbol andtransmitting the OFDM symbol through a radio channel or demodulating andchannel-decoding the OFDM symbol received through the radio channel andtransmitting the demodulated and channel-decoded OFDM symbol to thehigher layer. Further, the PHY layer uses hybrid ARQ (HARQ) to correctan additional error, and a receiving side transmits 1-bit informationindicating whether a packet transmitted by a transmitting side isreceived. The 1-bit information is referred to as HARQ ACK/NACKinformation.

Downlink HARQ ACK/NACK information for uplink transmission may betransmitted through a physical hybrid-ARQ indicator channel (PHICH), anduplink HARQ ACK/NACK information for downlink transmission may betransmitted through a physical uplink control channel (PUCCH) or aphysical uplink shared channel (PUSCH).

Meanwhile, the PHY layer may include one or a plurality offrequencies/subcarriers, and technology in which one eNB simultaneouslyconfigures and uses a plurality of frequencies is referred to as carrieraggregation (CA). CA significantly increases the amount of transmissionby the number of subcarriers by additionally using a primary carrier andone or a plurality of subcarriers, which is beyond the conventionaltechnology, in which only one subcarrier is used for communicationbetween the UE and the E-UTRAN NodeB (eNB).

Meanwhile, in LTE, a cell within the eNB using a primary carrier isreferred to as a Primary Cell (PCell) and a secondary carrier isreferred to as a Secondary Cell (SCell). The technology obtained byexpanding the CA function to two eNBs is referred to as dualconnectivity (DC). In the DC, the UE is simultaneously connected to anduses a master E-UTRAN NodeB (MeNB) and a secondary E-UTRAN NodeB (SENB),and cells belonging to the MeNB are referred to as a master cell group(MCG) and cells belonging to the SeNB are referred to as a secondarycell group (SCG).

Each cell group has a representative cell, and a representative cell ofa master cell group is referred to as a primary cell (PCell) and arepresentative cell of a secondary cell group is referred to as aprimary secondary cell (PSCell). When the NR is used, as the MCG usesLTE technology and the SCG uses NR, the UE may simultaneously use LTEand NT.

Although not illustrated, there is a radio resource control (RRC) layerabove the PDCP layer of each of the UE and the eNB, and the RRC layermay transmit and receive an access- and measurement-relatedconfiguration control message to control radio resources. For example,measurement may be indicated to the UE through the RRC layer message andthe UE may report the measurement result to the eNB through the RRClayer message.

FIG. 3C illustrates the concept of dual connectivity.

When the DC is used, the UE may be simultaneously connected to and usetwo eNBs. In FIG. 3C, a UE 3 c-05 is simultaneously connected to a macroeNB 3 c-00 using LTE technology and a small cell eNB 3 c-10 using NRtechnology and transmits and receives data. This is referred to asE-UTRAN NR dual connectivity (EN-DC).

The macro eNB is referred to as a master E-UTRAN Node B (MeNB) and thesmall call eNB is referred to as a secondary 5G node B (SeNB). There maybe a plurality of small cells within a service area of the MeNB, and theMeNB is connected to the SgNBs through a wired backhaul network 3 c-15.A set of serving cells provided from the MeNB is referred to as a mastercell group (MCG) 3 c-20, and one serving cell in the MCG is necessarilya primary cell (PCell) 3 c-25 having all functions performed by theexisting cell, such as connection establishment, connectionre-establishment, and handover.

In the PCell, an uplink control channel has a PUCCH. Serving cells otherthan the PCell are referred to as secondary cells (SCells) 3 c-30. FIG.3C illustrates a scenario in which the MeNB provides one SCell and theSgNB provides three SCells. A set of serving cells provided by the SgNBis referred to as a secondary cell group (SCG) 3 c-40.

When the UE transmits and receives data to and from the two eNBs, theMeNB provides the SgNB with commands for adding, changing, and removingserving cells provided by the SgNB. In order to transmit the commands,the MeNB may configure the UE to measure the serving cell andneighboring cells. The UE should report the measurement result to theMeNB according to configuration information.

For efficient data transmission and reception to and from the UE by theSgNB, a serving cell which plays a similar role to the PCell of the MCGis required and the serving cell is referred to as a primary SCell(PSCell) in the present disclosure. One the serving cells of the SCG isdetermined as the PSCell, and the PSCell has a PUCCH which is an uplinkcontrol channel. The PUCCH is used when the UE transmits HARQ ACK/NACKinformation, channel status information (CSI), and a scheduling request(SR) to the eNB.

FIG. 3D illustrates an example of a message flow between the UE and eNBswhen the UE starts measuring different types of RATs in the state inwhich eNBs using a plurality of RATs proposed by the present disclosurescoexist.

In FIG. 3D, a UE 3 d-01 in an idle mode (RRC_IDLE) accesses an LTE celldue to the generation of data to be transmitted in step 3 d-11. In theidle mode, the UE is not connected to the network to save power of theUE, so the UE cannot transmit data. In order to transmit data, the UE isrequired to switch to a connected mode (RRC_CONNECTED). When the UEsuccessfully accesses the LTE cell 3 d-03, the UE switches to theconnected mode (RRC_CONNECTED) and the connected-mode UE can transmitand receive data to and from the LTE cell through security activationand bearer configuration for data.

Thereafter, the eNB configures, in the UE, measurement of cells adjacentto the UE in step 3 d-13. The measurement configuration may include ameasurement object (measObject), a report configuration, a measurementstart condition, and measurement interval information for otherfrequency measurement.

The measurement object may include information indicating whichfrequency will be measured, and the frequency information may include anLTE frequency. If the UE supports NR or supports DC with NR, an NRfrequency may be included. The eNB may configure a plurality ofmeasurement objects in the UE.

The report configuration may include a configuration for periodicallyreporting the measurement result to the eNB or for reporting themeasurement result to the eNB when the following conditions aresatisfied.

-   -   Event A1 (the case in which serving cell measurement result is        better than threshold value)    -   Event A2 (the case in which serving cell measurement result is        worse than threshold value)    -   Event A3 (the case in which neighboring cell measurement result        is better than primary cell (PCell) (representative cell when        the UE uses a plurality of serving cells) measurement result by        offset or more)    -   Event A4 (the case in which neighboring cell measurement result        is better than threshold value)    -   Event A5 (the case in which primary serving cell (PCell)        measurement result is worse than threshold value 1 and        neighboring cell measurement result is better than threshold        value 2)    -   Event A6 (the case in which neighboring cell measurement result        is better than secondary cell (SCell) (remaining cells other        than PCell when the UE uses a plurality of serving cells)        measurement result by offset or more)

The eNB may configure the plurality of report configurations in the UE.

The eNB groups the measurements and the report configurations andmanages them through measurement identifiers. For example, when the eNBconfigures three measurement objects (for example, frequencies X, Y, andZ) and two report configurations (for example, report configuration 1:periodic report and report configuration 2: conditional report A3) inthe UE, the eNB may map report identifier 1 to frequency X and reportconfiguration 1 and map report identifier 2 to frequency Y and reportconfiguration 2 and configure the same in the UE.

The measurement start condition (s-Measure) is one threshold value. Whenthe signal intensity of the PCell, among the serving cells, is higherthan the measurement start condition, the UE determines that the signalintensity of the currently accessed cell is good enough and does notmeasure neighboring cells. By configuring the measurement startcondition, the UE does not unnecessarily measure neighboring cells,thereby reducing power consumption of the UE.

Meanwhile, in the state of the EN-DC, even though the channel state ofthe LTE PCell is good, it may be better not to stop measurement for NRneighboring cells. For example, if the UE uses the LTE PCell and thenadds the NR cell to the SCG (that is, NR SCell addition), even thoughthe channel state of the PCell is good, it may be preferable tocontinuously measure the NR cell to add the NR cell to the NR SCG intime. In another example, if there is an NR cell (providing a bettertransmission rate) near the UE while the UE uses the LTE PCell, it maybe preferable to perform handover to the corresponding NR cell in timewhen the handover is possible. Accordingly, for the example scenario,the present disclosure includes additional information other than thes-Measure. For the additional information, for example, three schemesmay be considered.

-   -   Scheme 1: indicator included for each measurement object        (measObject)

The measurement object (frequency) included in the indicator is measuredeven when the signal intensity of the PCell is higher than theconfigured s-Measure.

-   -   Scheme 2: second s-Measure (applied only to NR)

When the second s-Measure is configured, the second s-Measure is usedfor determining whether to measure frequencies belonging to the SCG (forexample, NR) or configured by the SCG.

In this case, the second s-Measure is included in the measurementconfiguration information configured by the NR SCG when EN-DC isconfigured in the UE.

-   -   Scheme 3: indicator included in the measurement configuration        information in common.

In this case, the corresponding indicator is commonly applied tofrequencies using a predetermined RAT technology (for example, NR).

The eNB may transmit various measurement configurations to the UEthrough an RRCConnectionReconfiguration message of the RRC layer.Thereafter, the UE transmits an acknowledgement message of theconfiguration indication in step 3 d-15, in which case the UE may use anRRCConnectionReconfigurationComplete message of the RRC layer.

The UE receiving the measurement configuration information measures thesame frequency as that of the current serving cell (intra-frequency), adifferent frequency (inter-frequency), and a frequency on whichdifferent types of RATs (inter-RAT) are used according to the configuredinformation and determines whether to perform a report in step 3 d-17.

At this time, the UE performs the following operation according to eachof the schemes.

If the UE receives the configuration of the indicator for each frequencyaccording to scheme 1 and the signal intensity (reference signalreceived power (RSRP)) of the PCell is smaller than the configureds-Measure value, the UE measures neighboring cells according toconfiguration information. However, if the RSRP of the PCell is higherthan the configured s-Measure value, the UE does not measure a frequencywhich does not include the indicator, but measures a frequency includingthe indicator.

If the UE receives the configuration of a second s-Measure valueaccording to scheme 2 and the signal intensity of the PCell is smallerthan the existing s-Measure (referred to as a first s-Measure), the UEstarts measuring a frequency on which RATs (for example, LTE, UMTS, andGSM) other than NR are used. When the signal intensity of the PCell ishigher than the first s-Measure, the UE does not measure the frequencyon which RATs (for example, LTE, UMTS, and GSM) other than NR are used.Meanwhile, the UE starts measuring NR when the signal intensity of thePCell is smaller than the second s-Measure and does not measure NR whenthe signal intensity of the PCell is higher than the second s-Measure.

In another embodiment, although not illustrated in FIG. 3D, the seconds-Measure value may be configured through the SCG (SgNB) 3 d-05. Thatis, in the state in which the SCG is added to the UE, the measurementinformation may be directly configured by the SCG and, at this time, thesecond s-Measure value may be included. In this case, the UE determineswhether to measure a frequency configured to be measured by the MCGusing the first s-Measure and determine whether to measure a frequencyconfigured to be measured by the SCG (or a frequency using the same RATas the RAT used by the SCG) using the second s-Measure value.

When the UE receives the configuration of a predetermined indicatorincluded in common in the measurement configuration informationaccording to scheme 3, the UE measures neighboring cells according tothe configuration information if the signal intensity (reference signalreceived power (RSRP)) of the PCell is smaller than the configureds-Measure value. However, if the RSRP of the PCell is higher than theconfigured s-Measure value, the UE measures a frequency using aseparately indicated or pre-appointed RAT (for example, NR) but does notmeasure other RAT and LTE frequencies.

According to the rule, the UE measures neighboring cells. When theconfigured report configuration is satisfied, the UE generates ameasurement report message in step 3 d-19 and transmits the same to theeNB in step 3 d-21. The eNB receiving the measurement report message maydetermine whether to add the reported cell to the SCell or performhandover to the reported cell according to the content contained in themeasurement report message. For example, by comparing the signalintensity of the current (LTE) PCell with the signal intensity ofneighboring NR cells (with a predetermined offset for normalizing abandwidth difference), the eNB may determine whether to add the NR cellto the SCG or to perform handover.

When the UE supports the DC and it is determined that the eNB adds theNR cell to the SCG for the UE according to the determination, the eNBtransmits SCG information to configure the DC function to the UE in step3 d-25. The SCG configuration information may include addition andrelease information of SCells added to the SCG. The SCG configurationinformation may be transmitted using an RRCConnectionReconfigurationmessage of the RRC layer.

Thereafter, the UE may transmit an acknowledgement message indicatingreception of the configuration information, and the message may betransmitted using an RRCConnectionReconfigurationComplete message instep 3 d-27. Accordingly, the UE may simultaneously transmit and receivedata using both the LTE cell 3 d-03, which is the MCG, and the NR cell 3d-05, which is the SCG, in step 3 d-29 and step 3 d-31.

FIG. 3E is a flowchart illustrating the operation of the UE when thepresent disclosure is applied.

In FIG. 3E, it is assumed that the UE is connected to the LTE eNB and isthus in a connected mode (RRC_CONNECTED) in step 3 e-01.

Thereafter, the UE receives a configuration of measurement ofneighboring cells from the eNB in step 3 e-03. The measurementconfiguration may include a measurement object (measObject), a reportconfiguration, a measurement start condition, and measurement intervalinformation for other frequency measurement.

The measurement object may include information indicating whichfrequency will be measured and the frequency information may include anLTE frequency. If the UE supports NR or supports DC with NR, an NRfrequency may be included. The configuration information may include aplurality of measurement objects.

The report configuration may include a configuration for periodicallyreporting the measurement result to the eNB or for reporting themeasurement result when the following conditions are satisfied.

-   -   Event A1 (the case in which serving cell measurement result is        better than threshold value)    -   Event A2 (the case in which serving cell measurement result is        worse than threshold value)    -   Event A3 (the case in which neighboring cell measurement result        is better than primary cell (PCell) (representative cell when        the UE uses a plurality of serving cells) measurement result by        offset or more)    -   Event A4 (the case in which neighboring cell measurement result        is better than threshold value)    -   Event A5 (the case in which primary serving cell (PCell)        measurement result is worse than threshold value 1 and        neighboring cell measurement result is better than threshold        value 2)    -   Event A6 (the case in which neighboring cell measurement result        is better than secondary cell (SCell) (remaining cells other        than PCell when the UE uses a plurality of serving cells)        measurement result by offset or more)

Further, the configuration information may include a plurality of reportconfigurations.

The configuration information may include configuration information forgrouping the measurement objects and the report configurations accordingto the measurement identifier.

The measurement start condition (s-Measure) is one threshold value. Whenthe signal intensity of the PCell, among the serving cells, is higherthan the measurement start condition, the UE determines that the signalintensity of the currently accessed cell is good enough and does notmeasure neighboring cells. By configuring the measurement startcondition, the UE does not unnecessarily measure neighboring cells,thereby reducing power consumption of the UE.

Meanwhile, in the state of the EN-DC, even though a channel state of theLTE PCell is good, it may be better not to stop measurement for NRneighboring cells. For example, if the UE uses the LTE PCell and thenadds the NR cell to the SCG (that is, NR SCell addition), even thoughthe channel state of the PCell is good, it may be preferable tocontinuously measure the NR cell to add the NR cell to the NR SCG intime. In another example, if there is an NR cell (providing a bettertransmission rate) near the UE while the UE uses the LTE PCell, it maybe preferable to perform handover to the corresponding NR cell in timewhen the handover is possible. Accordingly, for the example scenario,the present disclosure includes additional information other than thes-Measure. For the additional information, for example, three schemesmay be considered.

-   -   Scheme 1: indicator included for each measurement object        (measObject)

Measurement is performed in the case of the measurement object includingthe indicator or when the signal intensity of the PCell is larger thanthe configured s-Measure.

-   -   Scheme 2: second s-Measure (applied only to NR)

When the second s-Measure is configured, the second s-Measure is usedfor determining whether to measure frequencies belonging to the SCG (forexample, NR) or configured by the SCG.

In this case, the second s-Measure is included in the measurementconfiguration information configured by the NR SCG when EN-DC isconfigured in the UE.

-   -   Scheme 3: indicator included in the measurement configuration        information in common.

In this case, the corresponding indicator is commonly applied tofrequencies using a predetermined RAT technology (for example, NR).

The UE may receive various measurement configurations through anRRCConnectionReconfiguration message of the RRC layer. Thereafter, theUE transmits an acknowledgement message of the configuration indication,in which case the UE may use an RRCConnectionReconfigurationCompletemessage of the RRC layer.

The UE receiving the measurement configuration information measures thesame frequency as that of the current serving cell (intra-frequency), adifferent frequency (inter-frequency), and a frequency on whichdifferent types of RATs are used (inter-RAT) according to the configuredinformation and determines whether to provide a report in step 3 e-05.

At this time, the UE performs the following operation according to eachof the schemes.

If the UE receives the configuration of the indicator for each frequencyaccording to scheme 1 and the signal intensity (reference signalreceived power (RSRP)) of the PCell is smaller than the configureds-Measure value, the UE measures neighboring cells according toconfiguration information. However, if the RSRP of the PCell is higherthan the configured s-Measure value, the UE does not measure a frequencywhich does not include the indicator, but measures a frequency includingthe indicator.

If the UE receives the configuration of a second s-Measure valueaccording to scheme 2 and the signal intensity of the PCell is smallerthan the existing s-Measure (referred to as a first s-Measure), the UEstarts measuring a frequency on which other RATs (for example, LTE,UNITS, and GSM) other than NR are used. When the signal intensity of thePCell is higher than the first s-Measure, the UE does not measure thefrequency on which other RATs (for example, LTE, UMTS, and GSM) otherthan NR are used. Meanwhile, the UE starts measuring NR when the signalintensity of the PCell is smaller than the second s-Measure and does notmeasure NR when the signal intensity of the PCell is higher than thesecond s-Measure.

Although another embodiment is not illustrated in FIG. 3E, the seconds-Measure value may be configured through the SCG (SgNB). That is, inthe state in which the SCG is added to the UE, the measurementinformation may be directly configured by the SCG, at which time thesecond s-Measure value may be included. In this case, the UE determineswhether to measure a frequency configured to be measured by the MCGusing the first s-Measure and determine whether to measure a frequencyconfigured to be measured by the SCG (or a frequency using the same RATas the RAT used by the SCG) using the second s-Measure value.

If the UE receives the configuration of a predetermined indicatorincluded in common in the measurement configuration informationaccording to scheme 3, the UE measures neighboring cells according tothe configuration information when the signal intensity (referencesignal received power (RSRP)) of the PCell is smaller than theconfigured s-Measure value. However, if the RSRP of the PCell is higherthan the configured s-Measure value, the UE measures a frequency using aseparately indicated or pre-appointed RAT (for example, NR) but does notmeasure other RAT and LTE frequencies.

According to the rule, the UE measures neighboring cells. When theconfigured report configuration is satisfied in step 3 e-07, the UEgenerates a measurement report message and transmits the same to the eNBin step 3 e-09.

Thereafter, according to the report from the eNB, the UE may receive SCGinformation and configure the DC function or receive an instruction ofhandover to the corresponding cell in step 3 e-11. The SCG configurationinformation may include addition and release information of SCells addedto the SCG. The SCG configuration information may be transmitted usingan RRCConnectionReconfiguration message of the RRC layer.

Thereafter, the UE may transmit an acknowledgement message indicatingreception of the configuration information and the message may betransmitted using an RRCConnectionReconfigurationComplete message.Further, in the case of handover, the acknowledgement message may betransmitted to the moved cell. Accordingly, when DC is configured in theUE, the UE may transmit and receive data simultaneously using both theMCG and the SCG.

FIG. 3F is a block diagram illustrating the UE according to anembodiment of the present disclosure.

Referring to FIG. 3F, the UE includes a radio-frequency (RF) processingunit 3 f-10, a baseband processing unit 3 f-20, a storage unit 3 f-30,and a controller 3 f-40.

The RF processing unit 3 f-10 performs a function for transmitting andreceiving a signal through a wireless channel, such as band conversionand amplification of a signal. That is, the RF processing unit 3 f-10up-converts a baseband signal provided from the baseband processing unit3 f-20 into an RF band signal, transmits the RF band signal through anantenna, and then down-converts the RF band signal received through theantenna into a baseband signal. For example, the RF processing unit 3f-10 may include a transmission filter, a reception filter, anamplifier, a mixer, an oscillator, a digital-to-analog convertor (DAC),an analog-to-digital convertor (ADC), and the like. Although only oneantenna is illustrated in FIG. 3E, the UE may include a plurality ofantennas.

The RF processing unit 3 f-10 may include a plurality of RF chains.Moreover, the RF processing unit 3 f-10 may perform beamforming. For thebeamforming, the RF processing unit 3 f-10 may control the phase andsize of each signal transmitted/received through a plurality of antennasor antenna elements.

The baseband processing unit 3 f-20 performs a function of performingconversion between a baseband signal and a bitstream according to thephysical layer standard of the system. For example, in datatransmission, the baseband processing unit 3 f-20 generates complexsymbols by encoding and modulating a transmission bit string. In datareception, the baseband processing unit 3 f-20 reconstructs a receptionbitstream by demodulating and decoding a baseband signal provided fromthe RF processing unit 3 f-10. For example, in anorthogonal-frequency-division-multiplexing (OFDM) scheme, when data istransmitted, the baseband processing unit 3 f-20 generates complexsymbols by encoding and modulating a transmission bitstream, maps thecomplex symbols to subcarriers, and then configures OFDM symbols throughan inverse fast Fourier transform (IFFT) operation and a cyclic prefix(CP) insertion.

Further, in data reception, the baseband processing unit 3 f-20 dividesthe baseband signal provided from the RF processing unit 3 f-20 in unitsof OFDM symbols, reconstructs the signals mapped to the subcarriersthrough a fast Fourier transform (FFT) operation, and then reconstructsthe reception bitstream through demodulation and decoding.

The baseband processing unit 3 f-20 and the RF processing unit 3 f-10transmit and receive signals as described above. Accordingly, thebaseband processing unit 3 f-20 and the RF processing unit 3 f-10 may bereferred to as a transmitter, a receiver, a transceiver, or acommunication unit. Further, at least one of the baseband processingunit 3 f-20 and the RF processing unit 3 f-10 may include differentcommunication modules to process signals in different frequency bands.The different frequency bands may include a super-high-frequency (SHF)(for example, 2.5 GHz and 5 GHz) band and a millimeter (mm) wave (forexample, 60 GHz) band.

The storage unit 3 f-30 stores data such as a basic program, anapplication program, and setting information for the operation of theUE.

The controller 3 f-40 controls the overall operation of the UE. Forexample, the controller 3 f-40 transmits and receives a signal throughthe baseband processing unit 3 f-20 and the RF processing unit 3 f-10.The controller 3 f-40 records data in the storage unit 3 f-40 and readsthe data. To this end, the controller 3 f-40 may include at least oneprocessor. For example, the controller 3 f-40 may include acommunication processor (CP), which performs control for communication,and an application processor (AP), which controls a higher layer such asan application program. According to an embodiment of the presentdisclosure, the controller 3 f-40 includes a multi-connection processingunit 3 f-42 for performing processing in a multi-connection mode. Forexample, the controller 3 f-40 may control the UE to perform theprocedure of the operation of the UE illustrated in FIG. 3E.

According to an embodiment of the present disclosure, the UE receives amessage for instructing measurement from the eNB. The controllerreceiving the message determines whether to start measurement accordingto the configuration of a measurement event and condition received fromthe eNB, performs the measurement, and when the measurement is startedand the report configuration is satisfied, generates a correspondingmeasurement result report message and transmits the same to the eNB.

Methods stated in claims and/or specifications according to variousembodiments may be implemented by hardware, software, or a combinationof hardware and software.

When the methods are implemented by software, a computer-readablestorage medium for storing one or more programs (software modules) maybe provided. The one or more programs stored in the computer-readablestorage medium may be configured for execution by one or more processorswithin the electronic device. The at least one program may includeinstructions that cause the electronic device to perform the methodsaccording to various embodiments of the present disclosure as defined bythe appended claims and/or disclosed herein.

The programs (software modules or software) may be stored innon-volatile memories including a random access memory and a flashmemory, a Read Only Memory (ROM), an Electrically Erasable ProgrammableRead Only Memory (EEPROM), a magnetic disc storage device, a CompactDisc-ROM (CD-ROM), Digital Versatile Discs (DVDs), or other type opticalstorage devices, or a magnetic cassette. Alternatively, any combinationof some or all of these may form a memory in which the program isstored. Further, a plurality of such memories may be included in theelectronic device.

In addition, the programs may be stored in an attachable storage devicewhich may access the electronic device through communication networkssuch as the Internet, Intranet, Local Area Network (LAN), Wide LAN(WLAN), and Storage Area Network (SAN) or a combination thereof. Such astorage device may access the electronic device via an external port.Further, a separate storage device on the communication network mayaccess a portable electronic device.

In the above-described detailed embodiments of the present disclosure, acomponent included in the present disclosure is expressed in thesingular or the plural according to a presented detailed embodiment.However, the singular or plural expressions are selected to be suitablefor proposed situations for convenience of description, and the presentdisclosure is not limited to the singular or plural elements. An elementexpressed in a plural form may be configured in singular, or an elementexpressed in a singular form may be configured in plural.

Meanwhile, while the disclosure has been shown and described withreference to specific embodiments thereof in the detailed description ofthe present disclosure, it goes without saying that various changes inform and details may be made therein without departing from the spiritand scope of the disclosure. Therefore, the scope of the presentdisclosure should not be defined as being limited to the embodiments,but should be defined by the appended claims and equivalents thereof.

1-15. (canceled)
 16. A method by a terminal in a wireless communicationsystem, the method comprising: receiving, from a base station, a systeminformation block (SIB) 1 including scheduling information associatedwith other system information (SI) and at least one resourceconfiguration for requesting at least one other SI which is notbroadcasted; identifying a resource configuration corresponding tospecific SI from the at least one resource configuration, based on thescheduling information; and transmitting, to the base station, a requestfor the specific SI using the identified resource configuration.
 17. Themethod of claim 16, wherein identifying a resource configurationcorresponding to specific SI comprises: identifying whether the specificSI is not broadcasted based on the scheduling information; andidentifying the resource configuration corresponding to the specific SIfrom the at least one resource configuration, in case that the specificSI is not broadcasted.
 18. The method of claim 16, wherein the at leastone resource configuration includes first information associated with anindex of a preamble for requesting at least one other SI, and secondinformation associated with a resource where the preamble is to betransmitted.
 19. The method of claim 18, further comprising:transmitting, to the base station, a request for all of the other SIwhich are not broadcasted, based on one resource configuration includedin the SIB
 1. 20. The method of claim 18, further comprising:transmitting, to the base station, a request for first SI of the otherSI which is not broadcasted, based on a first resource configuration ofthe at least one resource configuration; and transmitting, to the basestation, a request for second SI of the other SI which is notbroadcasted, based on a second resource configuration of the at leastone resource configuration.
 21. A method by a base station in a wirelesscommunication system, the method comprising: transmitting, to aterminal, a system information block (SIB) 1 including schedulinginformation associated with other system information (SI) and at leastone resource configuration for requesting at least one other SI which isnot broadcasted; and receiving, from the terminal, a request forspecific SI based on the scheduling information, wherein a resourceconfiguration corresponding to the specific SI is identified by theterminal from the at least one resource configuration.
 22. The method ofclaim 21, wherein the resource configuration corresponding to thespecific SI is received, in case that the specific SI is notbroadcasted.
 23. The method of claim 21, wherein the at least oneresource configuration includes first information associated with anindex of a preamble for requesting at least one other SI, and secondinformation associated with a resource where the preamble is to betransmitted.
 24. The method of claim 23, further comprising: receiving,from the terminal, a request for all of the other SI which are notbroadcasted, based on one resource configuration included in the SIB 1.25. The method of claim 23, further comprising: receiving, from theterminal, a request for first SI of the other SI which is notbroadcasted, based on a first resource configuration of the at least oneresource configuration; and receiving, from the terminal, a request forsecond SI of the other SI which is not broadcasted, based on a secondresource configuration of the at least one resource configuration.
 26. Aterminal in a wireless communication system, comprising: a transceiver;and a controller configured to: control the transceiver to receive, froma base station, a system information block (SIB) 1 including schedulinginformation associated with other system information (SI) and at leastone resource configuration for requesting at least one other SI which isnot broadcasted; identify a resource configuration corresponding tospecific SI from the at least one resource configuration, based on thescheduling information; and control the transceiver to transmit, to thebase station, a request for the specific SI using the identifiedresource configuration.
 27. The terminal of claim 26, wherein thecontroller is further configured to identify whether the specific SI isnot broadcasted based on the scheduling information; and identify theresource configuration corresponding to the specific SI from the atleast one resource configuration, in case that the specific SI is notbroadcasted.
 28. The terminal of claim 26, wherein the at least oneresource configuration includes first information associated with anindex of a preamble for requesting at least one other SI, and secondinformation associated with a resource where the preamble is to betransmitted.
 29. The terminal of claim 27, wherein the controller isfurther configured to control the transceiver to transmit, to the basestation, a request for all of the other SI which are not broadcasted,based on one resource configuration included in the SIB
 1. 30. Theterminal of claim 27, wherein the controller is further configured tocontrol the transceiver to transmit, to the base station, a request forfirst SI of the other SI which is not broadcasted, based on a firstresource configuration of the at least one resource configuration; andcontrol the transceiver to transmit, to the base station, a request forsecond SI of the other SI which is not broadcasted, based on a secondresource configuration of the at least one resource configuration.
 31. Abase station in a wireless communication system, comprising: atransceiver; and a controller configured to: control the transceiver totransmit, to a terminal, a system information block (SIB) 1 includingscheduling information associated with other system information (SI) andat least one resource configuration for requesting at least one other SIwhich is not broadcasted; and control the transceiver to receive, fromthe terminal, a request for specific SI based on the schedulinginformation, wherein a resource configuration corresponding to thespecific SI is identified by the terminal from the at least one resourceconfiguration.
 32. The base station of claim 31, wherein the resourceconfiguration corresponding to the specific SI is received, in case thatthe specific SI is not broadcasted.
 33. The base station of claim 31,wherein the at least one resource configuration includes firstinformation associated with an index of a preamble for requesting atleast one other SI, and second information associated with a resourcewhere the preamble is to be transmitted.
 34. The base station of claim32, wherein the controller is further configured to control thetransceiver to receive, from the terminal, a request for all of theother SI which are not broadcasted, based on one resource configurationincluded in the SIB
 1. 35. The base station of claim 32, wherein thecontroller is further configured to control the transceiver to receive,from the terminal, a request for first SI of the other SI which is notbroadcasted, based on a first resource configuration of the at least oneresource configuration; and control the transceiver to receive, from theterminal, a request for second SI of the other SI which is notbroadcasted, based on a second resource configuration of the at leastone resource configuration.